UVC-based advanced oxidation processes for simultaneous removal of microcontaminants and pathogens from simulated municipal wastewater at pilot plant scale

The challenge of providing good quality reclaimed water free from contaminants of emerging concern, even at small concentrations, i.e., microcontaminants (MCs), and pathogens are one of the main hot topics worldwide. UVC based advanced oxidation processes, using in situ production of strong oxidizing radicals, such as HO^● and SO₄^●–, have shown high oxidation rates for MCs; however, few works have focused on the simultaneous removal of MCs and pathogens, like bacteria. Thus, the aim of this work was to assess the oxidation of six MCs: acetaminophen (ACT), caffeine, (CAF), carbamazepine (CBZ), trimethoprim (TMP), sulfamethoxazole (SMX), and diclofenac (DCF) in the presence of Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Salmonella enteritidis (S. enteritidis) in a simulated effluent from a municipal wastewater treatment plant by the application of UVC/H₂O₂ and UVC/S₂O₈^2– processes at pilot plant scale. The concentration of MCs and bacteria were monitored along the oxidation processes as well as their regrowth after 24, 48, and 144 h. UVC based processes were compared in terms of the required treatment time to remove at least 80% of the sum of MCs, regrowth assessment, and energy consumption. Despite UVC/H₂O₂ and UVC/S₂O₈^2– processes showed similar results, even though after using distinct molar concentrations, UVC/H₂O₂ process did not exhibit bacterial regrowth in dark conditions. A simple model has been also proposed in this work with the main objective of calculating the minimum concentration of oxidants as a function of the radiation absorption at 254 nm in a given photo-reactor setup.